I’ve used them for a 2S driver for the 6V MT-G2 here: Mod/build: MT-G2 & dual Nichia 219C headlamp
They are basically 7135s rated for 12V. Maybe they can handle a little more. I might give a go at seeing weather they can handle 16V for a 4S configuration (XHP-35 HI), but a buck driver would probably be a better solution.